a printer problem

[DE@PHOENIX.SCH.Symbolics.COM (Doug Evans)]

    Date: Mon, 16 Sep 1991 11:14 PDT
    From: h133mar%ella.hu@Warbucks.AI.SRI.COM (Markus Andras)

    subject: a printer problem

    Dear Slug,

	 [ . . . . ]

    following  way:  When  attempting  to  print  sg, the printer gets
    stuck, seen by peek as  "serial unit locked".  Having entered  the
    debugger and typed in s-C for detaching and resetting the printer,
    lisp stops itself by double-bit  error.  

This is your major problem.  Double bit errors are a hardware problem
and will cause a machine crash every time.  

First you need to determine the board causing the double bit error.
The error status should report a slot address between 0 and 31.  If
slot 31 is reported, then the PROCESSOR board is at fault and should be
replaced or repaired.  You can scan the TESTS FLOD and run the TEST
A-MEMORY command to test for problems in the processor's ALU section.

If it is not slot 31, note the number.  Then reset the FEP and do a
HELLO command.  Note the reporting after the INITIALIZE HARDWARE
TABLES command.  If the problem slot is reported as assigned to a
particular memory board, then that board is the problem board.  You can
scan the TESTS FLOD and run the TEST SIMPLE MAIN MEMORY command to
test for problems on memory boards.

If the problem slot is not reported, do a SHOW CONFIGURATION command
and look to see if a board is reported in the problem slot.  If the
problem slot matches a board, that board is the problem and should be
replaced or repaired.

If after all this, you still haven't matched the problem slot to a board,
it probably matches an empty slot ... which says the memory controller
on the PROCESSOR board is bad.